The background art is described below by taking a shovel as an example.
As shown in FIG. 6, the shovel includes: a lower propelling body 1 of a crawler type, an upper slewing body 2 provided on the lower propelling body 1 so as to be able to slew about a vertical axis with respect to the ground surface; a work attachment 9 which is installed on a front portion of this upper slewing body 2 by means of a boom foot pin 13; and a control valve 28 (see FIG. 9) which controls driving of the work attachment 9. The work attachment 9 includes a boom 3, an arm 4, a bucket 5, and hydraulic cylinders (namely, a boom cylinder, an arm cylinder and a bucket cylinder) 6, 7, 8 which operate the boom, arm and bucket, respectively.
As shown in FIG. 6 and FIG. 7, the upper slewing body 2 includes an upper frame 10 forming a base platform, and a left and right pair of vertical plates 11, 12 which are provided in an intermediate portion of the upper frame 10 in the left/right direction. The vertical plates 11, 12 are disposed at an interval apart in the left/right direction, and are also provided through substantially the whole length of the upper frame 10 in the front/rear direction.
As shown in FIG. 8, the front portions of each of the vertical plates 11, 12 project upwards in a shape of mountain. The boom foot pin 13 is provided at the front portions of the vertical plates 11, 12, so as to pass horizontally through the vertical plates 11, 12 in the left/right direction. The base end portion of the boom 3 is installed rotatably with respect to the vertical plates 11, 12 by means of the boom foot pin 13. Consequently, the boom 3 (the whole of the work attachment 9) can be raised and lowered about the boom foot pin 13.
As shown in FIG. 7, an engine compartment 15 of which the upper surface is opened and closed by a maintenance bonnet 14 is provided in a rear portion of the upper frame 10. An engine 16, which is a motive power source, and peripheral equipment of the engine (a radiator 17, a cooling fan 18, a hydraulic pump 19, etc.) are disposed in this engine compartment 15.
On the other hand, a cabin 20 is disposed in the space above the upper frame 10, to one side in left/right direction with respect to both vertical plates 11, 12, and to the forward side of the engine compartment 15 (in general, the cabin 20 is disposed to the left-hand side of the vertical plates 11, 12, hereinafter this case is described), and furthermore, a fuel tank 21 and a hydraulic oil tank 22 are arranged in a front/rear direction, to the other side in left/right direction with respect to both vertical plates 11, 12. Moreover, up-and-down steps 23 which enable a worker carrying out maintenance tasks to ascend to and descend from the bonnet 14 (and the devices inside the engine compartment 15) are provided in the space above the upper frame 10, to the forward side of the fuel tank 21 (the right front portion of the upper frame 10). The up-and-down steps 23 are formed in the shape of rearward-ascending steps having a hollow center.
In this specification “front/rear” and “left/right” indicates directions from the perspective of an operator seated in the cabin 20.
Furthermore, FIG. 7 and FIG. 8 show views with the work attachment 9 removed.
FIG. 9 shows a block composition of a drive system and a control system when the shovel is constituted as a hybrid system.
The hybrid shovel has hybrid devices, in addition to the basic composition of the shovel described above. More specifically, the hybrid devices includes: a motor-generator 24 which is capable of operating as an electric generator and an electric motor, a slewing electric motor 25 which is a slewing drive source, a electric storage device 26, such as a secondary cell, a controller 27 which controls these elements, and a mechatronic controller 35 which controls the control valve 28 in coordination with the controller 27.
The motor-generator 24 is driven by the engine 16. More specifically, as shown in FIG. 7, the motor-generator 24 is arranged with respect to the hydraulic pump 19 and connected to the engine 16.
The hydraulic actuator 29 shown in FIG. 9 includes the hydraulic cylinders 6 to 8 described above and left/right propelling hydraulic motors (not illustrated). This hydraulic actuator 29 is driven by supplying hydraulic oil discharged from the hydraulic pump 19, via the control valve 28. A control valve 28 is provided respectively for each actuator, but in FIG. 9, the control valves 28 are depicted as a set of a plurality of control valves.
The slewing electric motor 25 is provided so as to face a slewing bearing 30 shown in FIG. 6 (see FIG. 7), and causes the upper slewing body 2 to slew by driving a slewing gear (not illustrated).
The electric storage device 26 is respectively connected to the motor-generator 24 and the slewing electric motor 25 by a plurality of electric power cables 31 which are indicated by the bold lines in FIG. 9.
The controller 27 executes the various control required in the hybrid shovel. More specifically, the controller 27 controls switching of the motor-generator 24 between operation as an electric generator and operation as an electric motor, as well as controlling the electric power generated by the motor-generator 24, the current supplied to the motor-generator 24, the torque of the motor-generator 24, charging and discharging of the electric storage device 26 in accordance with excessive shortfall in the generator output of the motor-generator 24, and driving/halting of the slewing electric motor 25, and the like.
Furthermore, the controller 27 includes an inverter 33 and a hybrid controller 34 connected to the inverter 33. The inverter 33 is respectively connected to the motor-generator 24 and the slewing electric motor 25 by signal cables 32, which are represented by dotted lines in the drawings.
The electric storage device 26 is connected directly to the hybrid controller 34.
The mechatronic controller 35 controls the control valves 28 in coordination with the hybrid controller 34, and in accordance with operation of an operation lever (not illustrated), or the like.
In this hybrid shovel, if the power required of the hydraulic pump 19 is great, then the engine output is supplemented by operating the motor-generator 24 as an electric motor by the charged electric power of the electric storage device 26. On the other hand, if the power required of the hydraulic pump 19 is small, then the electric power generated by the motor-generator 24 is accumulated in the electric storage device 26. Consequently, an energy-saving operation which is an essential feature of the hybrid system is performed.
Conventionally, among the hybrid devices which are mounted in a hybrid type shovel of this kind, the electric storage device 26 and the controller 27 (inverter 33, hybrid controller 34) are often arranged in the engine compartment 15 (see Patent Documents 1 and 2, for example). Alternatively, the electric storage device 26 and the controller 27 may be arranged in a distributed fashion in a plurality of locations on the upper frame using the free space.
However, due to strong demand for size reduction in shovels, there is no spare margin for free space in shovels. Consequently, arranging the hybrid devices in addition to the basic constituent elements of the shovel with a vehicle size that is equivalent to a normal shovel is extremely difficult, regardless of whether a concentrated arrangement or a distributed arrangement is adopted.
Furthermore, if the electric storage device 26 and the controller 27 are arranged forcibly in concentrated fashion in the engine compartment 15, then this obstructs the flow of air to the radiator 17, and/or gives rise to massive generation of heat by the electric storage device 26 and the controller 27. On the other hand, if the electric storage device 26 and the controller 27 are arranged in distributed fashion, then this presents an impediment in that it makes assembly and maintenance of the machinery more troublesome.
Patent Document 1: Japanese Unexamined Patent Publication No. 2007-107230
Patent Document 2: WO 2008/015798